A099673 Partial sums of repdigits of A002280.

6, 72, 738, 7404, 74070, 740736, 7407402, 74074068, 740740734, 7407407400, 74074074066, 740740740732, 7407407407398, 74074074074064, 740740740740730, 7407407407407396, 74074074074074062, 740740740740740728, 7407407407407407394, 74074074074074074060, 740740740740740740726

Offset: 1

Author

Labos Elemer, Nov 17 2004

Keywords

• base
• nonn
• easy

Examples

			6 + 66 + 666 + 6666 + 66666 = a(5) = 74070.
		

Links

• Index entries for linear recurrences with constant coefficients, signature (12,-21,10).

Crossrefs

Cf. A002275-A002283, A014824, A057932, A099669-A099675.

Programs

Mathematica

<Robert G. Wilson v, Nov 20 2004 *)

Formula

a(n) = (2/27)*(10^(n+1) - 9*n - 10). - R. Piyo (nagoya314(AT)yahoo.com), Dec 10 2004

From Elmo R. Oliveira, Apr 02 2025: (Start)

G.f.: 6*x/((1 - x)^2*(1 - 10*x)).

a(n) = 6*A014824(n).

E.g.f.: 2*exp(x)*(10*exp(9*x) - 9*x - 10)/27.

a(n) = 12*a(n-1) - 21*a(n-2) + 10*a(n-3) for n > 3. (End)

Extensions

More terms from Elmo R. Oliveira, Apr 02 2025